Unless you can test the circuits to determine the failure and check for the predriver stage for any failure do not try to change. You must be familiar with the junctions, the type of the transistors before you try, they could be a complimentary pair driver too. so if familiar buy the same rating, desolder from the pcb, care to see for the correct junction, insert the Base, collector , emitter leads carefully solder and test after rechecking once again. otherwise get help.. Good day